This invention relates to a method and device for controlling pressure and flow rate.
In general, a cleaning method has widely been employed in the manufacturing process of a semiconductor production line in which such objects to be processed as semiconductor wafers and glass plates for LCD (hereinafter referred simply to wafer, etc.) are successively immersed in process tanks that include chemicals, cleaning solvents and other processing liquids. Such cleaning devices are provided with a drying device, in which the surface of cleaned wafers, etc. are exposed to dry gas consisting of volatile solvent, such as IPA (isopropyl alcohol), vapor to condense or adsorb the vapor, thus removing moisture on the wafers for drying.
FIG. 22 shows a typical drying device of this kind according to the prior art, which consists of a processing chamber "a" accommodating a plurality (e.g. 50 sheets) of wafers "W" and a steam generator "d" connected to the processing chamber "a" through a dried gas supply pipe line "c" communicating to a dried gas supply nozzle "b" disposed in the processing chamber "a". The dried gas supply pipe line "c" has an operating unit "j" therein, which consists of two parallel pipe lines "g" and "i". The first pipe line "g" includes a losing valve "e" and a needle valve "f", and the second pipe line "i" includes a losing valve "h". A supply source "k" of carrier gas (e.g. N.sub.2) and a supply source "m" of drying gas (e.g. isopropyl alcohol) are connected to the steam generator "d".
To prevent wafers from damaging caused by an abrupt supply of drying gas into the processing chamber "a" so as to bring the pressure of the processing chamber "a" (which has been depressurized) to a target pressure (e.g., atmospheric pressure), the drying device of this kind according to the prior art has following two steps: The first step opens the valve "e" and the needle valve "f" in the first line "g" to supply a small amount of drying gas into the processing chamber "a". Then, the second step opens the valve "h" in the second line "i" to supply the drying gas into the processing chamber "a".
However, because, as soon as the valve "e" is opened in the first step, the drying gas flows into the processing chamber "a" which has been depressurized with one atmospheric pressure differential, as shown in FIG. 23, the opening of the valve "e" creates a spike-like high-speed flow. The created spike-like high-speed flow causes particles to rise, resulting in attaching to wafers "W". Further, also when the first line "g" is switched over the second line "i", the spike-like high-speed flow is created in the same way, thus causing similar phenomenon.
Furthermore, also when a relatively large flow rate of drying gas supply is required in the processing chamber "a" under the target pressure such as atmospheric pressure, the large flow rate of drying gas supply into the processing chamber "a" may create a similar spike-like high-speed flow, thus resulting not only in causing the similar problem, but also in damaging of wafers "W" caused by the vibration.
In addition to the above dry processing, such problems as described above may arise in, for example, general systems in which fluids are supplied in a depressurized processing chamber, such as film making devices which make film under vacuum atmosphere. Furthermore, in cases where the processing chamber is over the target pressure such as atmospheric pressure, when the pressure is too abruptly depressurized, not only the gas in the processing chamber may instantly fluidized, thereby causing particles to rise, but also dew condensation of moisture in the gas due to its adiabatic expansion may cause particles to attach to wafers, etc.